Laser Surveys BIM ready models LASER SURVEYS. BIM Ready Models. A guide for our Clients. P a g e 1

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1 LASER SURVEYS BIM Ready Models A guide for our Clients P a g e 1

2 Introduction - the purpose of this guide: Survey information for the construction industry has a long-established tradition and is generally well understood by both Clients and Surveyors. The advent of BIM has led to presenting information in different formats and this document attempts to clarify what can, and cannot, be delivered. With an understanding of what is intended to be issued, a Client can adjust their order to ensure that the model will meet their needs. The Company: Laser Surveys was established in the Midlands in 1975 with our London office opening in We carry out all types of survey work throughout the mainland UK with our team of over 60 employees. Our Services: Topographical surveys, building surveys and underground services surveys are just part of what we do. We also supply digital datasets and reports, OS mapping, 3D Models, UAV surveys, historical mapping, geological and borehole information, and we have been providing BIM ready models since Experience: Over forty years of providing surveys using the latest surveying techniques. BIM Team: We have a team of dedicated Revit modellers in both our London and Worcester offices, allowing the size of the project team to be expanded to suit the workload. P a g e 2

3 Essential information for creating a BIM ready model: To meet our client s requirements we need to understand the following: 1. Which Grade of Detail of the Revit Model is required for the site, the building exterior and the building interior. If you want Phasing applied to the model. 2. If any 2D CAD drawings are also required. 3. If the Point Cloud data is required. 4. If the Survey is to be located on a local Datum and Grid or to the OS Datum and National Grid coordinate system. And as a Client you should also be aware of: 5. That the extent of the model is dependent upon the access that the surveyors are given. These items are identified on the Revit Deliverables part of our order form where our clients can select options and add comments or specific requirements. Each of these items is explained in more detail in the following sections. P a g e 3

4 1a-buildings GRADES OF DETAIL FOR BUILDINGS AND STRUCTURES Our simplified order form has four Grades of Detail for buildings and structures. GRADE B4 High Detail. Laser Surveys project specific families of doors, windows, stairs, ramps and balustrades. Project specific families based upon more detailed dimensions for fixtures, fittings, materials and architectural features. GRADE B3 Standard Detail. Laser Surveys generic families of doors, windows, stairs, ramps and balustrades. Generic families based upon overall dimensions for fixtures, fittings, and architectural features. GRADE B2 Outline Model. Overall shape of major walls, columns, floors, ceilings and roofs, with openings. GRADE B1 Massing Model. Overall shape of external building envelope. P a g e 4

5 ITEMS TO CONSIDER FOR GRADES OF DETAIL FOR BUILDINGS AND STRUCTURES Different grades of detail can be applied to the interior and the exterior, or to different buildings, or parts of buildings on the site. For example, on a refurbishment project the model may require a high grade of detail (B4) for the exterior, which is to be retained, but only an outline grade (B2) for the interior, which is to be stripped out. Consideration for grades B2, B3 and B4 should be identified for: Walls Cornices Dados Skirtings Floors Structural Columns and Beams Secondary Structural elements Ceilings and ceiling features Bulkheads Roofs, gutters and fascia s Windows and Curtain walling Doors and screens Stairs and handrailing Lifts and escalators Fixed furniture and fire surrounds Pipework and sanitaryware Building services Please identify on the order form if extra detailing to any of these is required. Where no specific requirements are identified for these then Laser Surveys standard modelling techniques will be used. A Revit phase of Existing can be applied. We do not normally do this unless a Client requests it. Phasing can make items appear, disappear and change colour, so unless it is used on a project we do not normally apply it. Often it is only practical to survey one side of an element (for example a ceiling) but a thickness is required to create an object in Revit. Where this is necessary the object properties will be named Wall/Floor/Ceiling/Roof of unknown thickness. Laser Surveys generic families are created in accordance with NBS BIM Object Standards in terms of geometry, behaviour and presentation. Metadata within the Laser Surveys generic families is compliant with the requirements for generic objects as specified within the BIM Object Standards. Clients can thus add in their own metadata, as information becomes available during the project, and the survey model would comply with the requirements for a COBie data drop. P a g e 5

6 1b-site GRADES OF DETAIL FOR TOPOGRAPHY The order form has a further three Grades of Detail for Site Topography. GRADE S3 Revit Toposurface with sub-regions and site features. Revit toposurface based on site level data points, and then divided into sub-regions to identify surface finishes. Site features such as steps, street furniture, barriers, retaining walls, and trees also modelled as Revit objects. GRADE S2 Revit Toposurface with sub-regions Revit toposurface based on site level data points, and then divided into sub-regions to identify surface finishes. GRADE S1 Revit Toposurface only Revit toposurface based on site level data points. P a g e 6

7 ITEMS TO CONSIDER FOR GRADES OF DETAIL FOR SITES AND TOPOGRAPHY Different grades can be applied to distinct parts of the site, for example stairs and ramps directly connected to a building may be required. Revit toposurfaces do not happily run vertically or fold back on themselves. It is often better to split surfaces at the top and bottom of kerbs. If this is not done, then Revit tries to join alternate top and bottom points giving a diamond shape to the edges. Kerbs are not modelled as Revit objects. Revit representations of trees and bushes are generic and only represent the approximate overall position, height and spread. The Point Cloud should be used as a data source for more exact geometry of such items. OTHER MODEL OUTPUT FORMATS AUTOCAD, IFC, MICROSTATION and SKETCHUP 3D models can by issued in a variety of formats including: Revit (RVT and RFA) AutoCAD 3D files (DWG) IFC files (for use with Vectorworks etc.) Microstation (DGN) SketchUp (SKP) The functionality of the model will depend on format in which the model is issued. RIGHTS OF LIGHT SURVEYS We regularly carry out Rights of Light surveys of specialist consultants where large areas are surveyed, in outline form, with door and window openings. These are far more accurate than the off the shelf data that is sometimes (but should not be) used. We can also produce this information with polylines around all openings allowing it to be used in the specialist analytical software used by Rights of Light Surveyors. P a g e 7

8 1c-above ground services GRADES OF DETAIL FOR ABOVE GROUND SERVICES We currently offer only one grade of detail for above ground services. GRADE A2 Services geometry modelled We will only model the overall size (including insulation) and position of above ground services, which will not contain the intelligent information usually incorporated into a BIM object. Support brackets and structures can be modelled, and generic valves and fittings can be included. P a g e 8

9 1d-below ground services GRADES OF DETAIL FOR BELOW GROUND SERVICS We offer only one grade of detail for below ground services GRADE B2 Services geometry modelled We will only model the approximate overall size and position of below ground services, which will not contain the intelligent information usually incorporated into a BIM object. Models include a zone of uncertainty which represents the limitation of accuracy of the detection equipment. Some assumptions are also made in order to make Revit objects, such as the thicknesses of buried walls and slabs. Not all underground services are detectable from surface scans. Modelling them in Revit does not improve the accuracy of what was surveyed with detection equipment. Where underground services are accessible we do offer a surveying and scanning service. Our surveyors have confined space training and we can arrange traffic management and escape teams for such works. P a g e 9

10 2-CAD output IN ADDITION TO THE REVIT MODEL WE CAN ALSO OFFER 2D CAD DRAWINGS IN DWG & DXF FORMATS 2D CAD 1:100 We can produce traditionally annotated 2D plans, ceiling plans, sections and elevations from the model for an additional cost. The annotation will include figured dimensions for ceiling heights, floor levels, window cill and head heights and door head heights. Beams and ceiling features will be shown as dotted lines. A client s linestyles and layering conventions can also be incorporated. Unannotated plans, sections and elevations can also be created at no extra cost. P a g e 10

11 3-point clouds THE ORIGINAL POINT CLOUD CAN BE SUPPLIED -OR ACCESS TO IT OVER AN INTERNET CONNECTION There are three options for including the Point Cloud as a Deliverable. This needs to be identified before the surveyor s visit site as it will affect the methodology used in the survey. Full colour point clouds add considerably to the amount of time spent on site, and consequently the cost of the survey. Point Cloud Options Black & White Supplied in AutoDesk Recap (RCS), Bentley MicroStation (POD) or E57 formats, usually via a Dropbox link. For exceptionally large files we issue point clouds on a memory stick for a small additional charge. Colour Supplied in AutoDesk Recap (RCS), Bentley MicroStation (POD) or E57 formats, usually via a Dropbox link. For exceptionally large files we issue point clouds on a memory stick for a small additional charge. Colour point clouds are more expensive but easier to interpret. Areas without lighting (such as loft spaces) must be scanned in black and white to obtain any detail. Applying colour to such spaces will result in a very dark or black point cloud. Webshare We can also host the point cloud data and give clients access to it from their phones, tablets or PC s. Users can inspect the survey, move around it and take levels and dimensions to any point. The advantage of this is that no specialist software is needed to inspect and interrogate the data. An annual charge is made for hosting the data, plus there is a nominal fee for uploading it initially. P a g e 11

12 4-positioning WHERE COLLABORATION IS IMPORTANT, AS IT IS WITH ALL BIM PROJECTS, A SHARED SURVEY POINT NEEDS TO BE AGREED A Datum, in surveying terms, refers to the vertical height (the z value) of a point. A Grid is established in plan view and refers to the vertical and horizontal positions (x and y values) of a point. Local Datum and Grid by Surveyor Our surveyors will establish a local datum and grid point for the survey and mark it on site and on the survey deliverables. Construction sites do often damage or obliterate such points, so they should not be relied upon to be there for the whole duration of the project. Local Datum and Grid by Client We can work from a defined point identified by Client, providing this can be identified to the surveyor upon their first visit to site. Ordnance Survey Datum and OS Grid. Many projects use the OS datum and OS Grid coordinates that cover the whole of the UK. These are usually annotated as Northings and Eastings for example: E,169990N for gridlines or E , N for individual points. Benchmarks are no longer verified or checked by the Ordnance Survey and are therefore rarely used as they may have moved. We use a satellite system to establish both Datum and Grid. Hybrid systems are also available e.g. an OS Datum can be used with a local Grid. We can accommodate these if we know our Clients requirements before we commence the survey works. P a g e 12

13 Revit True North and Project North. Revit has way of rotating a model without actually rotating it! It has options for displaying Project North and True North. True North in our models will depend upon which Positioning option has been selected earlier in this section, i.e. Local datum and grid by surveyor, Local datum and grid by client or OS datum and OS grid. Revit True North will align with the survey, which will align with whichever of those options has been chosen. Revit Project North can apparently rotate the model. This is useful where buildings are slightly askew, either to the vertical or horizontal planes. It can be apparently rotated, making drawing new walls much simpler. Rotating Project North does not alter the underlying coordinate system, which will still read correctly. It is important to establish this before modelling commences as moving or rotating a model afterwards, although not impossible, can be problematic. Please be aware that selecting True North in Revit will only orientate your view to OS North if you have told us that that is the way you wanted site surveyed, i.e. OS Datum and OS Grid. We include this on our order form and if left unanswered take the view that Revit Project North will be decided by the Surveyor, unless it has previously agreed with the Client or the Clients Architect. Using large coordinates Revit has problems with large coordinate numbers, but our surveys can be set up to OS Datum and Grid and other Revit files can then simply Acquire the coordinates from our survey. P a g e 13

14 Other Positioning Issues Repositioning a model after completion can be problematic as the point cloud and model are set to the same coordinate system before modelling commences. Projects are often initiated with an OS Mastermap plan or Title Deed information from the Land Registry. The latter relies on the former for its information, and the absolute accuracy of an OS Mastermap is: Scale RMSE* 95% confidence level 99% confidence level 1:1250 (urban) <±0.5m <±0.8m <±0.9m 1:2500 (rural) (resurvey or reformed) <±1.1m <±1.9m <±2.4m 1:2500 (rural) <±2.8m <±4.7m <±5.8m 1: (mountain and moorland) <±4.1m <±7.1m <±8.8m We discuss the accuracy of the survey in our Client guide to accuracy document and generally achieve better than ±25mm. Deed plans and OS maps are ±800mm in urban areas and ±1900mm in rural areas for a 95% confidence level. Hopefully this demonstrates the need for an accurate survey from a company such as ourselves at as early a stage as possible in the project. We cannot determine in law a boundary position, but we can accurately locate certain physical features to enable legal professionals to progress matters in the appropriate way. P a g e 14

15 5 - access Remember if you cannot see something from where you are standing (such as hidden pipework, columns or beams), it is likely that we cannot survey it. Survey as found The standard for most of our surveys. Areas cleared by client prior to survey. Existing items are removed and replaced by the client, for example ceiling tiles, if the structural floor depth needs to be measured. Specialist access equipment provided by client. If surveys are needed where safe access is not normally available, for example lift shafts, then the client may provide safe facilities to allow our surveyors to carry out their work. We also publish BIM Ready Models Client Guide to Accuracy should you wish to know more about the accuracy standards of our models. If you have any questions or comments about anything in this document, then please contact us. This document is copyright of Laser Surveys Ltd. and may not be reproduced in any form, in part or as a whole, without the written permission of Laser Surveys Ltd. t: +44 (0) e: worcester@lasersurveys.com Issue B 16/04/2018 P a g e 15